AU2020100158B4

AU2020100158B4 - An overflow device comprising or including a rainhead

Info

Publication number: AU2020100158B4
Application number: AU2020100158A
Authority: AU
Inventors: Rowan GREGORY; Russell John Kirkwood; David John Pockett
Original assignee: Dam Buster Ip Pty Ltd
Current assignee: Dam Buster Ip Pty Ltd
Priority date: 2016-02-19
Filing date: 2020-01-30
Publication date: 2020-09-24
Anticipated expiration: 2025-02-13
Also published as: AU2019203055B2; US11028593B2; AU2017200959B2; US20200347603A1; AU2020100158A4; AU2019100457B4; NZ758020A; AU2019100671B4; AU2019100671A4; AU2017200959A1; AU2019203055A1; AU2017100163A4; AU2019100457A4

Abstract

A rainhead flow control device comprises a mounting, external or front, and side walls, an internal wall between the mounting external or front wall and extending between the side walls, and a bottom wall extending between the side walls and between the mounting wall; the internal wall forming with the side, mounting and internal walls a tub defining an internal receptacle; and the bottom wall defining, or enabling a bottom wall outlet for engageing a downpipe. The internal, the side walls and external or front walls together define a chute having a chute outlet. The mounting wall defines receptor for a box gutter to enable water from the gutter to flow to the receptacle. The device is mountable so water is able to flow from the gutter to: - discharge into the downpipe, if the internal receptacle and the downpipe are unblocked; or - overflow the weir to discharge through the chute if one or each of the internal receptacle and the downpipe is blocked.

Description

AN OVERFLOW DEVICE COMPRISING OR INCLUDING A RAINHEAD

Field of the Invention

[001] This invention relates to an overflow device comprising or including a rainhead construction.

Background of the Invention

[002] The Australasian Standard AS/NZS 3500.3:2015 ('3500.3 Standard') Stormwater drainage code (titled Plumbing and drainage Part 3 Stormwater drainage) specifies and provides a respective illustration of three types of overflow device for box gutters, namely (a) a rainhead, (b) a sump/side overflow device and (c) a sump/high capacity overflow device. That 3500.3 Standard, as well as each subsequent edition specifies, in relation to a type (a) overflow device, that:

Rainhead denotes "A collector of rainwater, generally of rectangular shape, at the end of a box gutter and external to a building, connected to an external downpipe. It has a similar function to a sump."

[003] In contrast, the 3500.3 Standard and subsequent editions specifies, in relation to each of type (b) and (c) overflow device, that:

Sump denotes "A collector of rainwater, generally of rectangular shape, in the sole of a box gutter and connected to a downpipe within the building perimeter. Its function is to increase the head of water at the entry to the downpipe and thus increase the capacity of the downpipe."

[004] When a blockage occurs in a downpipe to which a rainhead is connected, the rainhead is intended to operate without an increase in the depth of water flow in the box gutter, even if operating up to its maximum design hydraulic capacity. Rather, water is required to overflow a wall forming a weir at the front of the rainhead and discharge to atmosphere. In contrast, a blockage that occurs in a downpipe to which a sump, of either type (b) or (c), is connected requires an increase in the depth of flow in the box gutter, up to the maximum design hydraulic capacity of the box gutter, in order for the sump device to allow overflow to occur. Thus, apart from some similarity in function, a rain head is installed and operates in a different manner to a sump.

[005] A sump typically is mounted in the sole of the box gutter, between successive lengths of the gutter, and on roofing within the perimeter of a building. In contrast, a rainhead is typically external to the building, above an external downpipe. Specifically, the rainhead is mounted on an external wall of the building, adjacent to the perimeter of the roofing and at an end of the box gutter.

[006] The present invention is directed to providing an improved overflow device comprising, consisting of or including a rainhead.

Broad Description of the Invention

[007] According to the present invention, there is provided a rainhead comprising:

an open topped tub member made of a metal and having a mounting wall, a front wall spaced from the mounting wall, opposed side walls fixed to and joining the mounting and front walls, and an inlet at an upper extent of the tub member,

an open topped internal receptacle and an open topped chute in the tub member, with the receptacle defined in part by the mounting wall, the side walls, and an upstanding or erect internal wall that joins the side walls and is common to the receptacle and the chute, and with the chute defined by the front wall, the side walls and the internal wall;

wherein:

- the tub member further includes a lower extent at which the tub member defines both (i) a bottom wall at which the receptacle is adapted or adaptable to be connected to communicate with a downpipe and (ii) a chute outlet; and - the rainhead is adapted at the mounting wall to be installed in relation to an external wall of a building, between an end of a box gutter section of guttering and an upper end of a downpipe of the building whereby: (a) in the absence of a blockage restricting the discharge of water through the bottom wall, all water from the box guttering is able to flow into the receptacle through the inlet and to discharge through the bottom wall to the downpipe; and (b) in the event of a blockage restricting the discharge of water through the bottom wall, water is able to rise in the receptacle to overflow an upper edge of the internal wall and to discharge substantially vertically in the chute and to drain through the chute outlet.

[007A] In one form of the rainhead of the invention an upper extent of the mounting wall is adapted to define a receptor by which the end of the box gutter section is receivable to enable water from the box gutter to flow through an inlet to the internal receptacle of the tub member. In that form, the chute outlet may be defined by or within the lower edges of the side walls, the front wall and the internal wall, or is defined between a bottom wall at the lower end of the chute and either at least one side wall or the front wall. The chute outlet may be defined by or within the lower edges of the side walls, the front wall and the internal wall, or is defined between a bottom wall at the lower end of the chute and either at least one side wall or the front wall. Also, an upper extent of the mounting wall may be adapted to define a receptor by provision of a gutter receptor attached to and forming the inlet to the receptacle of the tub member. A back plate may be fitted adjacent to the mounting wall, with the back plate defining or adapted to define a gutter receiver for box guttering of lesser width that the receptor of the mounting wall.

[008] The overflow device of the invention may operate in a similar manner to the prescribed rainhead illustrated in 3500.3 Standard (herein the "prescribed 3500.3 rainhead"). Under normal flow conditions up to the design hydraulic capacity of the box gutter, stormwater is able to discharge into the downpipe to which a rainhead is connected, and from the downpipe to flows unimpeded to an authorised point of discharge for the building via an underground stormwater drainage system. However, the overflow device of the invention differs significantly from the prescribed 3500.3 rainhead in that: a) The weir formed by the internal wall in the overflow device of the first aspect of the invention is concealed by the external wall, such that the weir is internal and not visible; b) If the downpipe is blocked, or its flow capacity is exceeded, water first overflows the internal, non-visible weir, potentially impacting with the external wall before discharging down to atmosphere through the chute outlet at the bottom of the rainhead. This is in contrast to the prescribed 3500.3 rainhead, as the latter causes the water to overflow the outer face of a front wall, comprising an external, visible weir, and thereby discharge to atmosphere; and c) As a consequence of the external wall of the overflow device, water overflowing the weir is redirected so as to have an almost downwards trajectory by the time it reaches then bottom of the overflow chute. In contrast, the prescribed 3500.3 rainhead, the overflowing water has an initially horizontal trajectory that alters increasingly beyond the weir to downwards, due to the force of gravity (that is, it has a trajectory similar to water spillingover a waterfall or spillway). In this regard, the chute defined between the internal wall and the external wall spaced from the internal wall accords substantially with the usual meaning of denoting a channel or passage enabling unimpeded flow, such that the chute outlet most preferably provides no impediment, or at least minimal impediment, to such flow.

[009] In addition to differences a) to c), the overflow device of the invention, at least in some forms, enables a secondary overflow provision. The latter provision is by an outlet or opening (typically rectangular, but other shapes, such as circular may be used) that is provided in the external wall and has sufficient capacity to operate as a supplementary overflow facility. However, it is likely to require extreme conditions, of both the downpipe and internal receptacle on the one hand and the weir and chute overflow provision on the other hand to be blocked, before such supplementary facility will be required. The overflow device is preferably proportioned such that the chute has adequate, or more than adequate, hydraulic capacity to discharge the water for the maximum design flowrate in the box gutter and rainhead. However, the overflow device could also be proportioned to have a relatively narrower chute, which would result in the primary overflow having a hydraulic capacity less than the design maximum flowrate, with the deficit in hydraulic capacity of the primary overflow then being provided by the secondary overflow. Most commonly, however, the primary overflow would be designed to have adequate, or more than adequate, hydraulic capacity, and the secondary overflow would not be required hydraulically. However, the secondary overflow could still be installed within the device for aesthetic reasons.

[010] In addition to these differences, the overflow device of the invention is considered to have a significant aesthetic advantage over the prescribed 3500.3 rainhead as the spacing between the internal and external walls that forms the chute effectively hides the end of the box gutter and the weir, other than a small portion that may be visible if an outlet/opening is provided in the external wall to enable a supplementary overflow facility. The overflow device of the invention is considered to be visually preferable device, and hence more likely to be selected by architects, building designers, building owners, developers, plumbers and the like, over a rainhead like the prescribed 3500.3 rainhead.

[011] The overflow device of the invention, at least in preferred forms, has a further substantial advantage in facilitating visual inspection from below (typically at ground level), as compared to commonly available rainheads. A check of whether the primary overflow outlet is blocked or clear can be conducted quickly and easily by an untrained person. As long as the primary overflow remains visually clear, the overflow device of the invention will continue to operate as intended in protecting the building from internal flooding. This is unlike previously proposed rainheads that requires access to the rainhead itself, or above it, for inspection purposes.

Thus, the invention has substantial Occupational Health and Safety benefits in association with routine maintenance and inspections.

[012] A downpipe is able to drain water from the internal receptacle by engagement of the upper end of the downpipe with the outlet provided in the base wall of the tub. The outlet preferably is preformed and of a size suited for engagement with a downpipe of a standard size. However, the outlet may be formed on site, such as to suit a previously installed downpipe, particularlywhere there is a need to allow an installer the option of cutting an outlet hole to fit a particular size or location of downpipe.

[013] The top of the internal wall most preferably is lower than the bottom of the inlet. The top of the internal wall also may be lower than an upper edge of each of opposite sides of the overflow device that extend from the mounting wall to the external wall, and also lower than an upper edge of the external wall. An upper edge of the internal wall that enables it to form or function as a weir may be sharply edged or rounded. The secondary overflow outlet, if provided, may have a bottom edge that is lower than the top of the internal wall, such as by about 25mm or more.

[014] Assuming that there is no blockage, the internal receptacle during normal flow conditions up to the design flow rate should be large enough to receive all water flowing through the inlet from a box gutter without the receptacle overflowing.

[015] The chute outlet most preferably is substantially directly in line with the chute. Where this is the case, the chute outlet may be defined by a lower edge of each of the front, internal and side walls. However, at least one of those edges may have a narrow flange that extends inwardly across the chute. In one form, each of the front, internal and side walls has such a flange, with the arrangement preferably such that the flanges of adjacent walls are contiguous to form a continuous flange around the periphery of the chute outlet. The flange, or each flange in aggregate, is such that the area of the chute outlet is a major part, such as at least 85% and preferably at least 90%, of the transverse cross-section of the chute. The chute outlet conveniently can be formed by cutting out an area, from a bottom wall provided across the lower end of the chute between the side walls and between the front and internal walls. The cut out area and, hence the chute outlet preferably is rectangular, although other arrangements are possible.

[016] The chute outlet may be other than in line with the chute. In that case the device may have a bottom wall across the lower end of the chute between the side walls and between the front and internal walls that, with the device in an in-use orientation, closes the lower end of the chute. In that event the chute outlet comprises an opening at or adjacent the lower end of the chute in at least one of the front wall and the side walls. In one convention arrangement, the chute outlet comprises an opening in one, or a respective opening in each, of the side walls such as an opening extending between the front and internal walls. In another convenient arrangement, the chute outlet comprises an opening in the front wall such as an opening extending between the side walls.

[017] The upper extent of the mounting wall maybe adapted in a number of different ways to define a receptor by which the box gutter end section is receivable to enable water flowing from the box gutter to be received through an inlet to the internal receptacle of the tub. In one way, the upper extent of the mounting wall is so adapted by provision of a gutter receptor attached to and forming the inlet to the receptacle of the tub. The gutter receptor preferably has a configured opening for receiving an end of a box gutter of a given standard width. However, a gutter receptor with a configured opening for receiving an end of a box gutter of the given standard width will not be suitable, or as suitable, for other a box gutter of different standard or a non-standard width, particularly if provision of effective sealing between the gutter receptor and gutter end is to be possible. Accordingly, as is known for use with a rainhead having such a gutter receptor, a back plate can be installed in the receptacle against the inner face of the mounting wall. The back plate is of sufficient height so as to cover the configured opening of the gutter receptor and it is suitably shaped to permit a good seal with the other box gutter. In another alternative, the mounting wall, or a back plate that has not been shaped, may have an upper edge on which the end of the box gutter is received to enable water to flow from the box gutter through the inlet to the internal receptacle of the tub. However, such alternative generally is found to be undesirable due to the difficulty of providing and effective seal and to it not being compatible with the required height for the overflow device relative to the end of the box gutter. In a further arrangement, a back plate can be installed between the outer surface of the mounting wall and its gutter receptor with the back plate cut and shaped to form a receiver within the receptor, with the receiver sized to receive a box gutter which has a width less than the gutter receptor. In this further arrangement, the back plate is cut and folded (or 'fashioned') to form vertical flanges of the receiver that are spaced so the box gutter of lesser width enables a good seal between that box gutter and the rainhead.

[018] In order that the invention may more readily be understood, description now is directed to the various embodiments of the invention illustrated in the accompanying drawings.

Brief Description of the Drawings

[019] Figure 1 is a sectional view of part of a building showing an overflow device according to the invention in a usual relationship to a box gutter, with the arrangement shown apart from the full drainage system of roofing of the building for which system the box gutter comprises a part;

Figure 2 is a perspective view of the overflow device and box gutter of the arrangement of Figure 1;

Figure 3 is an isometric view from above of the general form of an overflow device similar to that of Figure 1;

Figure 4 is an isometric view of the overflow device of Figure 3 taken from one side; Figure 5 is an isometric view of the overflow device of Figure 3 from below; Figure 6 is an isometric elevation view of the rainhead of Figure 3;

Figures 7 and 8 are isometric views of an alternative rainhead construction according to the invention;

Figure 9 shows nappe profiles downstream of a box gutter;

Figure 10 shows nappe profiles downstream of the internal wall of the rainhead device; and

Figures 11 to 14 show respective alternative forms of overflow device according to the invention.

Detailed Description of the Drawings

[020] With reference to Figures 1 and 2, there is shown an overflow device , comprising or consisting of a rainhead, according to a first aspect of the present invention. In Figure 1, the device 10 is shown as installed in relation to a building represented only by a section through a parapet wall Wa, an adjacent wall Wb and part of the structure of roofing R, for enabling water from the roofing to drain along a box gutter B within the roofing R. In the arrangement of Figure 1, the device 10 is mounted externally of the building on wall Wa, adjacent to a corner of the building defined by walls Wa and Wb, with the gutter G extending along the wall Wb. As seen in Figure 1, the device 10 is mounted on wall Wa adjacent to an end of the box gutter B that extends through a purpose-cut hole or opening H through wall Wa. The arrangement enables water to flow from the gutter G into an external downpipe 20 of the building, via the overflow device 10.

[021] With reference to Figures 3 to 7, the overflow device 10 comprises a tub 22 that includes a rear mounting wall 24, an internal wall 26 and a base portion 28. The arrangement is such that the tub 22 defines an internal receptacle 30 above the base portion 28, between mounting wall 24 and internal wall 26 and also between sidewalls 32 each of which extends between a respective edge of walls 24 and 26. The internal wall 26 forms a weir and the arrangement is such that water accumulating in receptacle is able to overflow the upper edge of wall 26 when the hydraulic capacity of the receptacle 30 and downpipe 20 is exceeded, or when either the receptacle 30 or downpipe 20 is blocked, or partially blocked (thereby reducing their hydraulic capacity). However, the base portion 28 defines an outlet 33 adapted for engagement with the upper end of downpipe 20 for the intended purpose of water draining from receptacle 30 through the downpipe 20 rather than overflowing the weir provided by wall 26.

[022] The overflow device 10 further includes a front, or external wall 34 spaced forwardly from the internal wall 26 and joining across extensions of the sidewalls 32. The arrangement is such that a chute 36 is defined between walls 26 and 34 and between sidewalls 32, with the chute 36 having a chute outlet 38 defined by the internal wall 26, the external wall 34 and the sidewalls 32. Thus, in the event that water does overflow the weir provided by wall 26, the water is able to discharge substantially unimpeded under gravity, through the chute 36 and the chute opening 38.

[023] The upper extent of mounting wall 24 is shaped to define, or is provided with, a gutter receptor 40 that forms an inlet 41 to the receptacle 30. As shown, the gutter receptor 40 forms a rectangular opening 42 in the upper extent of the mounting wall 24 with a horizontally extending flange 44 projecting from the lower edge of the opening 42, away from the internal wall 26, with a respective upright flange 46 extending similarly away from each side of the opening 42. The arrangement is such that the opening 42 and flanges 44 and 46 define the inlet 41 and receptor 40 is adapted to receive the end of the box gutter 16 to enable water flowing from the end of the gutter 16 to discharge into the receptacle and then through the outlet 33 of base portion 28 and into downpipe 20.

[024] The internal wall 26 has an upper edge that defines a weir 26a. The height of wall 26 is less than that of the external wall 34 and the sidewalls 32, and preferably not more than the height of the flange 44 that extends from the lower edge of opening 42 in the mounting wall 24.

[025] The overflow device 10 is adapted to be mounted externally of the building, with rear wall 24 of the device 10 located against the building wall 12. The device 10 is mounted at a location at which the device 10 is adjacent to an end section of the box gutter 16 that projects outwardly with respect to the roofing 14, into an opening 12a formed through the wall 12. At that location mounting wall 24 of the device is adjacent or against the wall 12 of the building with the flanges 44 and 46 received inwardly into the opening 12a. The arrangement is such that, within the opening 12a, the end section of gutter 16 is engaged received in the gutter receptor 40, with the receptor preferably shaped so that the channel shape of the gutter 16 is neat in the receptor 40 (apart from a small gap allowed for the installation of a silicone sealant), whereby, with the overflow device 10 so mounted, water is able to flow from the roof of the building to drain along the box gutter 16 to flow from the end of gutter, through the inlet 41 and into the receptacle 30. Thus, the water is able to discharge through the outlet 33 defined by the base portion 28, into the downpipe 20, if the receptacle 30 and the downpipe 20 are unblocked. However, if one or each of the receptacle 30 and the downpipe 20 is blocked, or partially blocked, or if, during an extreme rainfall event (i.e. having an intensity greater than the maximum design rainfall intensity), the hydraulic capacity of receptacle 30 and downpipe 20 are exceeded, or if the hydraulic capacity of the storm water drainage system downstream of the rainhead and downpipe is exceeded, water is able to fill receptacle 30 so as to overflow the weir 26a, to discharge through the chute 36 to overflow outside the building.

[026] As indicated, the chute 36 is defined between walls 26 and 34 and between sidewalls 32, with the chute outlet 38 defined by the internal wall 26, the external wall 34 and the sidewalls 32. The chute 36 is disposed upright, when the device is mounted as described, so that water is able to discharge through the outlet 38, in the event that water does overflow the weir provided by wall 26a, by the water passing through the chute 36 and the chute outlet 38 by substantially by unimpeded free-fall under gravity. Preferably the lower edge of at least the internal wall 26 is below the underside of base portion 28 so that the tendency for water to flow around the lower edge of wall 26 does not enable water to pass across the underside of portion 28 towards wall 12. This arrangement provides a 'drip edge', and its purpose is to prevent the flow of water laterally along a horizontal external surface to a vertical external surface, down which the flow or water can result in (unwanted) staining and/or water damage.

[027] As a precaution, should flow through both the internal receptacle 30 and the chute outlet 38 become blocked, such as by leaves or twigs or foreign objects, an overflow outlet 48 may be formed in the external wall

34. The overflow outlet 48 may be provided at a level at which its bottom edge is below the level of the weir defined by the internal wall 26, but above the calculated impact point of the free overflow from the internal wall 26 forming a weir. A more detailed explanation of the secondary overflow outlet 34 in the external wall 48 is provided earlier herein, prior to reference to the accompanying drawings.

[028] A moulding 49 may be provided around the upper extent of the external wall 34 and the sidewalls 32 both to lend rigidity, and to improve the aesthetics, of the device 10. To facilitate attachment of the rainhead to the side of the building, an attachment member 50 as shown in Figure 5 may optionally be provided in addition to the fixing lugs 51.

[029] The alternative construction shown in Figures 7 and 8 is generally the same as that for Figures 3 to 6 with the exception that the moulding 49A is provided internally of the tub 22.

[030] The following equations are utilized to compute the nappe profiles downstream of a box gutter, and of the internal wall 26, respectively. Downstream of the Box Gutter (Free Overfall)- See Figure 9:

Y - X gh ho V= 2VX

where Y

h, is the brink depth

v is the vertical velocity component at the brink

V is the horizontal velocity component at the brink

X =

ho is the uniform depth in the box gutter

x and y are horizontal and vertical coordinates of the upper nappe respectively.

Downstream of the Internal Wall (Sharp-Crested Weir) - See Figure 8.

y = (-0.425, + 0.055) + 0.15 + 0.559) H

where H is the upstream energy level (equivalent, in this case, to the upstream depth)

[031] The respective alternative forms of overflow device according to the invention shown in Figures 11 to 14 generally will be understood from the description of the device 10 of Figures 3 to 6. Corresponding components therefore are identified by the same reference numeral, plus 100 in the case of Figure 11, and 200, 300 and 400 in the case of Figure 12, 13 and 14, respectively.

[032] The overflow device 110 of Figure 11 differs from device 10 of Figure 3 to 6 in that mounting wall 124 is of rectangular form with a substantially horizontal upper edge 124a and without a formed gutter receptor corresponding to receptor 40 (with horizontal flange 44 and upright flange 46) of Figures 3 to 6. The wall 124 may be shaped, by removing a rectangular section along the dotted line on wall 124, to form a gutter receptor for accommodating an end of a box gutter from which water is able to flow into the receptacle of tub 122. Alternatively, while of lesser suitability, the upper edge 124a can function as a receptor on which the end of the box gutter is received to enable water to flow from the box gutter through the inlet to the internal receptacle of the tub 122.

[033] Rather than mounted to receive water from a box gutter, the device 110 can be adapted to receive water at one side wall 132 from a length of eaves guttering G or from each side wall 132 from a respective length of eaves guttering G. For this, a cut-out 154 and/or 154a is removed from an upper corner of the or each side wall 132, adjacent to mounting wall 124, to form a gutter receptor for laterally receiving an end of an eaves gutter length. The arrangement is such that water flows into the receptacle of the tub 122 for discharge through the receptacle outlet 133 unless such discharge is blocked. However, in the event of such discharge being blocked, water is caused to fill the receptacle, to overflow the weir 126 to discharge substantially vertically through the chute 136 and to drain through the chute outlet 138 to discharge to atmosphere.

[034] In the case of Figure 12, the sole difference of the device 210 from device 10 of Figures 3 to 6 is in the form of chute outlet 238. Whereas the chute outlet 28 in device 10 of Figures 3 to 6 is defined by a lower edge of each of the front, internal and side walls, the chute outlet 238 is bordered by a narrow flange on each of the front, internal and side walls, with the flanges of adjacent walls are contiguous to form a continuous flange 228a around the periphery of the chute outlet 238. The chute outlet 238 conveniently can be formed by cutting out an area, from a bottom wall provided across the lower end of the chute between the side walls and between the front and internal walls to leave the continuous flange 228a.

[035] The sole difference between device 310 of Figure 13 and device 10 of Figures 3 to 6 also is in the form of chute outlet 338. In device 310, a bottom wall 53 is provided below and across the lower end of the chute 336, between the side walls 332 and between the front wall 334 and internal wall 326. However, rather than an outlet being formed in the bottom wall 53, a respective chute outlet 338 is formed in each side wall 332, adjacent to the bottom wall 53. The arrangement is such that water falling vertically in the chute 336 is diverted to flow laterally through the respective one of chute outlets 338, 338a in each side wall 332.

[036] Figure 14 shows a device 410 that is a variant on the arrangement of device 310 of Figure 13. The device 410 has a bottom wall 54 provided across the lower end of the chute between the side walls 432, with the bottom wall curving downwardly and forwardly from the lower edge of the internal wall 426 to define a forward edge of the bottom wall 54 spaced below the lower edge of front wall 434. Thus the chute outlet 438 has an elongate form extending between the side walls 432 and between the opposed respective edges of the bottom wall 54 and the front wall 434.

The arrangement is such that water falling vertically in the chute 436 is diverted to flow forwardly through the chute outlet 438 beyond the front wall 434.

[037] Each flow control or overflow device 10, 110, 210, 310 and 410 comprising a rainhead may be constructed of any suitable material. It may be of a metal such as steel, stainless steel, COLORBOND or Zincalume protected steel, aluminium or copper. Alternatively, the device can be made of a suitable plastics material. Also, while the illustrated embodiment shows external box-shaped forms of overflow device, it is to be appreciated that while it usually is necessary for the mounting wall to be flat, the sidewalls and/or the external wall may be curved or bent. Indeed, the sidewalls may curve to merge into a curved front or external wall. A variety of configurations can be adopted to suit practical needs or aesthetic requirements that do not affect functioning of the overflow device.

[038] The relative dimensions of key features of the overflow devices described with reference to Figures 3 to 6, 7 and 8, and each of Figures 11 to 14 of the drawings will preferably be according to the prescribed 3500.3 rainhead. The dimensions can be chosen to comply with the requirements of the Australasian Standard AS/NZS 3500.3:2015 and subsequent editions, but are not limited to so complying. Those requirements require that the rainhead is physically sealed to the box gutter and has provision to overflow outside the building without restriction in up to a 1-in-a-100 year rain event. The rainhead may be sized to be slightly wider than the box gutter that it is servicing, such as to act as a cover plate around broken edges of masonry or render where the box gutter penetrates the outer wall of the building.

[039] The actual sizes of the rainhead suitable for the particular application and location of use will be determined based on the design flow rate for a given roof catchment area having a design rainfall intensity for a 1-in-a-100 year reoccurrence for a specific location in Australia as defined in AS/NZS 3500.3.

[040] Currently AS3500.3 limits the maximum flow rate of all overflow devices to 16 litres per second. The dimensions of an overflow device comprising or including a rainhead desirably are based on both engineering design and aesthetic considerations. The dimensions are not required to be limited to any specific flow rate, and can be designed (by engineering principles and / or physical testing) to accommodate substantially larger flow rates that the maximum of 16 litres per second currently prescribed by 3500.3.

[041] While the above description includes the preferred embodiments of the invention, it is to be understood that many variations, alterations, modifications and/or additions may be introduced into the constructions and arrangements of parts previously described without departing from the essential features or the spirit or ambit of the invention.

[042] It will be also understood that where the word "comprise", and variations such as "comprises" and "comprising", are used in this specification, unless the context requires otherwise such use is intended to imply the inclusion of a stated feature or features but is not to be taken as excluding the presence of other feature or features.

[043] The overflow device according to the invention that comprises or includes a rainhead has one or more features to facilitate overflow of water outside of a building even if a section of the rainhead becomes blocked. It also provides compliant overflow while maintaining a traditional rainhead aesthetic by means of the external wall of the rainhead able to shield against a direct line of sight into the end of the box gutter without impairing the ability of the rainhead to discharge overflow water if the rainhead outlet becomes blocked or if the flow of water is beyond the design capacity of the stormwater drainage system.

Claims

1. A rainhead comprising:

an open topped tub member made of a metal and having a mounting wall, a front wall spaced from the mounting wall, opposed side walls fixed to and joining the mounting and front walls, and an inlet at an upper extent of the tub member, an open topped internal receptacle and an open topped chute in the tub member, with the receptacle defined in part by the mounting wall, the side walls, and an upstanding or erect internal wall that joins the side walls and is common to the receptacle and the chute, and with the chute defined by the front wall, the side walls and the internal wall; wherein:

- the tub member further includes a lower extent at which the tub member defines both (i) a bottom wall at which the receptacle is adapted or adaptable to be connected to communicate with a downpipe and (ii) a chute outlet; and - the rainhead is adapted at the mounting wall to be installed in relation to an external wall of a building, between an end of a box gutter section of guttering and an upper end of a downpipe of the building whereby:

(a) in the absence of a blockage restricting the discharge of water through the bottom wall, all water from the box guttering is able to flow into the receptacle through the inlet and to discharge through the bottom wall to the downpipe; and (b) in the event of a blockage restricting the discharge of water through the bottom wall, water is able to rise in the receptacle to overflow an upper edge of the internal wall and to discharge substantially vertically in the chute and to drain through the chute outlet.

2. The rainhead of claim 1,wherein an upper extent of the mounting wall is adapted to define a receptor by which the end of the box gutter section is receivable to enable water from the box gutter to flow through an inlet to the internal receptacle of the tub member.

3. The rainhead according to claim 2, wherein the chute outlet is defined by or within the lower edges of the side walls, the front wall and the internal wall, or is defined between a bottom wall at the lower end of the chute and either at least a side wall or the front wall.

4. The rainhead according to claim 2 or claim 3, wherein an upper extent of the mounting wall is adapted to define a receptor by provision of a gutter receptor attached to and forming the inlet to the receptacle of the tub member.

5. The rainhead according to any one of claims 2 to 4, wherein a back plate is fitted adjacent to the mounting wall, with the back plate defining or adapted to define a gutter receiver for box guttering of lesser width that the receptor of the mounting wall.

20 Wa

H 1/13

FIG 1 B R Wb

42 2/13

FIG 2 40 B

2020100158 3/13

32 36 26a 48

30

49

46 38

44 26

41 33 10 40 32

46 3 28 51

FIG 3

2020100158 4/13

19 46 24 32 41

49 44 46

51

10

34 22

32

48

33 26 38

FIG 4

2020100158 5/13

48

34 36

38

26

28 49

10 32

51 33 50 40

44 46 FIG 5

FIG 5